1. Field of the Invention
Aspects of the present invention relate to a secondary battery, and more particularly, to a secondary battery that can combine a protection device with an insulation case by mechanical connection.
2. Description of the Related Art
Generally, a batteries used as a power source of electronic devices have become more important and have been actively developed with increased use of portable electronic devices such as cellular phones and portable personal digital assistants (PDAs) and digital cameras, etc. with the reduction in size of electric bicycles, electric cars and electric tools.
A lithium secondary battery has an operating voltage of 3.6V, which is three times more than that of a nickel-cadmium battery or a nickel-hydrogen battery that are usually used as a power source of electronic devices. In addition, the lithium secondary battery has higher energy density per unit weight. Accordingly, the lithium secondary battery has been widely used in the portable wireless devices as well as in various technology fields.
The lithium secondary battery typically includes a bare cell, a protection circuit board and a molded part or a case covering a portion where the bare cell and the protection circuit are electrically coupled to each other. The electrical coupling between the bare cell and the protection circuit is typically formed by using a conduction device called a lead plate, a protection device such as a thermal breaker or a bimetal, and an insulation sheet. Accordingly, the bare cell and the protection circuit board are electrically coupled to each other by welding separate connection members or elements to the bare cell or the protection circuit board, or welding them to each other. Particularly, the protection device is typically attached to the insulation case by using a double sided tape for preventing the protection device from being released from the insulation case. However, when the protection device is attached to the insulation case by the double sided tape, relatively precise and troublesome works are required and defect products are increased and productivity of the battery is reduced because of defects of electrical coupling of the battery. In addition, the attachment by the double sided tape is weak to external forces such as torsion or bending, thereby lowering safety.